Some conventionally known examples of metal film producing methods may include vapor deposition, sputtering, and ion plating, all of which are dry processes, and electroplating and electroless plating, both of which are wet processes. The dry process requires costly equipment. The wet process has difficulty in forming metal films with a thickness from a few tens to a few hundreds of nanometers.
Accordingly, there is a report about a technology of forming a metal film by: generating cation exchange groups through modification of a polyimide resin; then fixing metal ions to the cation exchange groups; and reducing the fixed metal ions. See patent document 1.
Patent Document 1: Japanese Unexamined Patent Publication No. 2001-73159 (Tokukai 2001-73159; published Mar. 21, 2001)